We have developed and utilized statistical methods and computer analysis of synaptic interactions between pairs of spinal cord (SC) cells and between dorsal root ganglion (DRG) cells and SC cells to study pre- and post-synaptic mechanisms in mammalian CNS cell cultures. Alterations in Ca ions and Mg ion ions primarily affect the output of transmitter in this system although minor post-synaptic effects may also occur. Catecholaminergic neurons from the locus coeruleus have been co-cultured with spinal cord cells. Preliminary experiments indicate that physiologically functional interactions develop between the catecholaminergic cells and post-synaptic SC cells. Radioautography of SC-DRG and cerebral cortical cultures indicates that 125I-tetanus toxin and 3H-GABA labeling are primarily neuronal, whereas 3H-beta-ananine labeling is primarily non-neuronal.